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The so called take-off and emergency rating (Start- und Notleistung 1.42ata) of the DB605A engine of the early Me109G was forbidden to use until late 1943 afaik. Does anybody know if it was allowed to use so-called climb and combat rating (Steig- und Kampfleistung 1.3 ata) for 30 minutes with these derated engines or was the maximum permissable duration for this power setting also decreased?

There's an English translation of the original German order forbidding 1.42 ata floating around. Try WWII Aircraft Performance

It says that on older engines, and it gives worknumbers to identify which, the 1.3 ata climb and combat rating must be used only when operationally essential.

Click to expand...

Unfortunately on this page there is only a translation by british intelligence and not the original quote in german. But it would be extremely interesting what "operationally essential" means in this respect. As long as you dogfighting a spitfire - for a brief boost to break away from a fight - use it freely in air combat but not when cruising just to reach your destination faster ???? There is a wealth of possible interpretations.

Well, the fact that aircraft with strengthened pistons did not have the warning about only when operationally essential suggests that there was some risk in running at 1.3 ata in the older engines. It doesn't look like a fixed time limit, but they are only guidelines anyway.

Basically, if you were prepared to risk your engine blowing you could use it as long as you liked

I found the text you referred to in the section about comparing 109G with Spitfire MkIX. There only older engines were mentioned and that the problem why not to use 1.42 ata was due to pistons burning through. Where can I find the source that newer engines have stronger pistons not making them able to be used safely with 1.42 ata but making the hint to only use 1.3 ata "when operationally essential" obsolete. Is a longer portion of the text available somewhere on Mike William's page?

I'm not sure what's on Mike Williams site, but I have what I think is the complete teleprinter message as a scan (probably from Mike, or Neil Sterling).

I won't type in the whole thing, but the relevant bits are:

"The Take-off and emergency output with a boost pressure of 1.42 atm. and 2800 revs. may not at present by used. The climbing and combat output with 1.3 atm. and 2600 revs. may in the case of the older engines (for works numbers see below), be used only when operationally essential." (that's from Mike's site)

It goes on later:
"In engines with reinforced pistons the danger of their burning through is not so great as in the older version of the piston, but the takeoff and emergency output may still not be used."

There's more saying older pistons will be replaced in refit, so I think the problem with 1.3 ata would have disappeared as time went on, unless some new problem occurred.

The captured transmission effectively speaks about the greater wear of the pre-production DB 605A-0 engines, not the serial production DB 605A-1.

1,42ata appears to have been cleared in 8 June 1943, and used operationally at Kursk, however it seems they were not entirely satisfied and recalled the clearance until Daimler-Benz finally brought a fix in September 1943 by installing oil de-aerators, which seems to be the root of the problem (bubbles forming in oil, reducing lubrication to nil).

The captured transmission effectively speaks about the greater wear of the pre-production DB 605A-0 engines, not the serial production DB 605A-1.

1,42ata appears to have been cleared in 8 June 1943, and used operationally at Kursk, however it seems they were not entirely satisfied and recalled the clearance until Daimler-Benz finally brought a fix in September 1943 by installing oil de-aerators, which seems to be the root of the problem (bubbles forming in oil, reducing lubrication to nil).

In any case, all engine and aircraft manuals which still note the ban on Notleistung give 30-minute limit for Kampfleistung just the same.

I'm not sure what's on Mike Williams site, but I have what I think is the complete teleprinter message as a scan (probably from Mike, or Neil Sterling).

I won't type in the whole thing, but the relevant bits are:

"The Take-off and emergency output with a boost pressure of 1.42 atm. and 2800 revs. may not at present by used. The climbing and combat output with 1.3 atm. and 2600 revs. may in the case of the older engines (for works numbers see below), be used only when operationally essential." (that's from Mike's site)

It goes on later:
"In engines with reinforced pistons the danger of their burning through is not so great as in the older version of the piston, but the takeoff and emergency output may still not be used."

There's more saying older pistons will be replaced in refit, so I think the problem with 1.3 ata would have disappeared as time went on, unless some new problem occurred.

Click to expand...

HOP,
any chance you can scan and post here the original teleprinter message?
Does anyone has it?
Thanks for help,
Gatt

Roger that. We (the Targetware-Target Tobruk MODers) are researching what happened in the Regia Aeronautica and Aeronautica Repubblicana (after september 1943) as far as the 1,42ata, 2.800rpm limit is concerned.

The DB605A was mounted on the C.205, the G.55 and the Re.2005, however we dont know if and when the limit was canceled. So far, we discovered only one manual, the 1944 G.55's one, without any limitation.